The present invention relates to improvements in a clamping device used for semipermanently fixing a fluid conveying hose, dustproof bellows, axial boot or the like made of a plastic material, such as rubber or synthetic resin, to the connecting circumferential surface of a desired mating device.
The so-called open type clamping device is known wherein a clamp band of metal strip material cut to a fixed length is wound into a circular ring with one end overlapping the other, whereby said clamp band is three-dimensionalized, the bore diameter being then artificially forcibly contractively deformed and the opposite ends locked together, a rubber hose for conveying various fluids is connected to the cylindrical mouthpiece portion of a joint pipe, cock or the like. Lobe-formed clamping devices called Oetiker are well known in the art. In this clamping device, as suggested from U.S. Pat. Nos. 3,082,498; 3,286,314; 3,402,436; 3,789,463; 4,299,012; and 4,315,348, the circumferential surface of the clamp band is formed with one or two bridge type lobes integrally projecting therefrom, the arrangement being such that the lobes are squeezed and crushed by an exclusive tool to reduce the bore diameter.
In that case, although the clamp band does not develop springiness to expand or contract in circumferential direction, since said rubber hose to be fixed is usually made of a rubber material having a relatively low hardness (elasticity) with a Shore hardness of about 60 or less, the clamp band closely contacts the rubber hose throughout the circumferential surface thereof; thus, the rubber hose or the like can be held on a desired mating device in a stable tightened state without any danger of deviation or slipping off.
However, parts to be fixed, such as dustproof bellows and axial boots which are blow-molded from thermoplastic synthetic resin material have a high hardness, such as a Shore hardness of 90 or more, lacking in elasticity itself. Thus, such part can hardly be stably and firmly tightened on the connecting circumferential surface of a desired mating device. Particularly, when it is used for a vehicle which is subjected to torques, vibrations and shocks, there is a danger of causing deviation and slipping off.
Even if the clamp band of said lobe-formed clamping device is further formed with a number of locking teeth and receiving holes besides said lobes to allow the bore diameter of the expandable clamp band to be adjustable, since the lobes are squeezed by a tool in the final stage subsequent to the engagement between the locking teeth and the receiving holes, there will be excess or deficiency of the bore diameter reducing force unless the amount of squeeze is properly determined to suit the thickness of the part to be fixed; thus, a stable firm tightened state cannot be maintained. Further, if the squeezing force and crushing force on said lobes are cancelled, the lobes will spring back in the direction to open, thus aggravating the above problem.
Further, such problem occurs not only in said parts made of synthetic resin with high hardness but also in parts made of rubber having elasticity. In the latter case, if the elasticity is lost owing to aging with the lapse of time, a similar problem occurs, making it impossible to maintain the service durability in the tightened state.
Further, in the lobe-formed clamping device, since it is used with the lobes crushed, there is a merit that the lobes do not rise high above the circumferential surface of the camp band. On the other hand, there is a demerit that the weight distribution is extremely localized, so that if the clamping band is used for an apparatus which rotates at high speed, the clamping force provided by the clamping band does not uniformly act on the circumferential surface of the part, with local weakness in the clamping force being produced.